1. Field of the Invention
The present invention relates to an electrostatic discharge (ESD) protection device to protect a semiconductor device, etc. from electrostatic discharge failures, and a method for manufacturing such an ESD protection device.
2. Description of the Related Art
In recent years, for the use of commercial-off-the-shelf appliances, there has been a tendency to increase the frequency of inserting and removing cables as input-output interfaces, and consequently, static electricity is likely to be applied to input-output connector areas. In addition, miniaturization in design and increases in signal frequency have made it difficult to create paths, and LSI itself has been highly sensitive to static electricity.
Therefore, ESD protection devices have been used widely for protecting semiconductor devices such as LSI from electrostatic discharge (ESD).
As this type of ESD protection device, an ESD protection device (chip-type surge absorber) including an insulating chip body which has an enclosed space with an inert gas encapsulated in the center, opposed electrodes each having a microgap in the same plane, and external electrodes, and a method for manufacturing the ESD protection device have been proposed (see Japanese Patent Application Laid-Open No. 9-266053).
However, in the ESD protection device (chip-type surge absorber) in Japanese Patent Application Laid-Open No. 9-266053, electrons need to jump directly across the microgaps of the opposed electrodes without any assistance, and the discharge capacity of the ESD protection device thus depends on the microgap width. Furthermore, the more the microgaps are narrowed, the more the capacity as a surge absorber is increased. However, the width of a gap has a limitation in the formation of opposed electrodes with the use of a printing method as described in Japanese Patent Application Laid-Open No. 9-266053, and an excessively narrow gap results in problems such as the opposed electrodes being connected to each other to cause a short circuit defect.
In addition, as described in Japanese Patent Application Laid-Open No. 9-266053, a cavity section is formed by stacking perforated sheets. Thus, considering that there is a need to provide a microgap in the cavity section, the reduction in size of the product also has a limitation in terms of stacking accuracy. Furthermore, in order to provide the enclosed space filled with an encapsulating gas, there is a need to carry out stacking and pressure bonding under the encapsulating gas upon stacking, thus leading to the problems of a complicated manufacturing process, a decrease in productivity, and an increase cost.
Furthermore, as another ESD protection device, an ESD protection device (surge absorbing element) provided with internal electrodes electrically connected to a pair of external electrodes and a discharge space within an insulating ceramic layer including the external electrodes, and with a discharge gas trapped in the discharge space, and a method for manufacturing the ESD protection device have been proposed (see Japanese Patent Application Laid-Open No. 2001-43954).
However, the ESD protection device in Japanese Patent Application Laid-Open No. 2001-43954 also have the same problems as the ESD protection device in Japanese Patent Application Laid-Open No. 9-266053 mentioned above.